1. Field of the Invention
The present invention relates to a motor magnetic-pole-position estimating apparatus.
2. Description of the Related Art
A conventionally known apparatus for, for example, a synchronous motor having saliency is an apparatus that calculates a phase difference by using that an induced voltage changes in accordance with a phase, based on a voltage equation of control axes (dc-qc coordinate axes) having a phase difference with respect to dq coordinate axes of real axes, and calculates the phase of the control axes from the calculation result (for example, see Japanese Patent Laid-Open No. 2001-251889).
Unfortunately, the apparatus according to the conventional technique cannot calculate the phase difference at a low rotation speed including a situation in which the motor is stopped. The phase difference has to be calculated by another operation method.
Owing to this, for example, the apparatus may include a plurality of arithmetically operating devices that calculate phase differences by a plurality of different operation methods, so that the plurality of arithmetically operating devices are switched in accordance with the rotation speed of the motor to calculate a phase difference. However, apparatus configuration may be complicated, and operation load increases, resulting in that chattering occurs when the plurality of arithmetically operating devices are switched.